Photopolymerization and Aza-Michael click addition for highly homogeneous photopolymer networks and smart materials

Ahmad Ibrahim, University of Haute Alsace

Abstract: The ability to form polymeric networks with dynamic control of polymerization reactions is a challenging research field. Indeed, this could participate to broaden the range of applications and lead to significant technological developments [1]. Introduced by Sharpless and al. [2], the “click chemistry” is an attractive concept for polymer tailoring [1]. Using this chemistry, polymers may be easily generated without solvents and heat while giving rise to high yields [2]. Recently, by selecting the thiol-Michael addition as a click reaction, a two-stage system has been elegantly designed to produce smart materials [3].

In this study, a click chemistry synthetic strategy based on aza-Michael addition and radical photopolymerization is proposed to generate a polymeric network via three time-controlled steps: 1/AZ1: primary diamines add stoichiometrically on diacrylates double-bonds to form a quasi linear polymer, 2/hν: photopolymerization of the unreacted double-bonds and 3/AZ2: in situ generated secondary amines add on trapped residual diacrylates double-bonds to achieve a highly cross-linked polymer [4]. Consequently, the second aza-Michael addition appears as a valuable postconsolidation step of the polymer network. The key feature of the process is the reduction of dangling ends by AZ2 that enabled high-density cross-linking and more uniform response of the polymer chains to thermal stimuli. The range of potential monomer structures would make this process versatile and open up new horizons. SMP can be designed for a vast range of applications as thermomechanical and shape memory properties are tailorable [5, 6].